The invention relates generally to phosphorescent iridium complex(es), polymers that incorporate the complexes in a main chain or as end groups, and optoelectronic devices containing the complexes and polymers.
Organic light emitting devices (OLEDs), which make use of thin film materials that emit light when subjected to a voltage bias, are expected to become an increasingly popular form of flat panel lighting and display technology. This is because OLEDs have a wide variety of potential applications, including cellphones, personal digital assistants (PDAs), computer displays, informational displays in vehicles, television monitors, as well as light sources for general illumination. Due to their bright colors, wide viewing angle, compatibility with full motion video, broad temperature ranges, thin and conformable form factor, low power requirements and the potential for low cost manufacturing processes, OLEDs are seen as a future replacement technology for cathode ray tubes (CRTs) and liquid crystal displays (LCDs). Due to their high luminous efficiencies, OLEDs are seen as having the potential to replace incandescent, and perhaps even fluorescent, lamps for certain types of applications.
Light emission from OLEDs typically occurs via electrofluorescence, i.e. light emission from a singlet excited state formed by applying a voltage bias across a ground state electroluminescent material. It is believed that OLEDs capable of producing light by an alternate mechanism, electrophosphorescence, i.e. light emission from a triplet excited state formed by applying a voltage bias across a ground state electrofluorescecent material, will exhibit substantially higher quantum efficiencies than OLEDs that produce light primarily by electrofluorescence. Light emission from OLEDs by electrophosphorescence is limited since the triplet excited states in most light emitting organic materials are strongly disposed to non-radiative relaxation to the ground state. Thus, electrophosphorescent materials hold promise as key components of OLED devices and other optoelectronic devices exhibiting greater efficiencies relative to the current state of the art. For example, OLEDs capable of light production by electrophosphorescence are expected to exhibit a reduction (relative to OLEDs which produce light primarily by electrofluorescence) in the amount of energy lost to radiationless decay processes within the device thereby providing an additional measure of temperature control during operation of the OLED.
Improved light emission efficiencies have been achieved by incorporating a phosphorescent platinum-containing dye in an organic electroluminescent device such as an OLED (See Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices”, Nature, vol. 395, 151-154, 1998) and phosphorescent iridium-containing dyes have also been employed (See for example Lecloux et al. United States Patent Application 20030096138, May 22, 2003). Notwithstanding earlier developments, there is currently considerable interest in finding novel phosphorescent materials which not only increase efficiency but also provide for a greater measure of control of the color of light produced by an OLED. For example, it would be highly desirable to provide novel phosphorescent materials which enable organic electroluminescent devices having improved overall efficiency, while at the same time allowing for the light output to be red shifted or blue shifted, depending on the nature of the application.